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Ignoring the numerous forms of undefined behavior that casting away const might invoke, the blunt but simple and standard solution is just to cast to (void*). char* foo (const char* str) { r...
Answer
#2: Post edited
by
Lundin
·
2022-06-15T19:55:13Z (over 2 years ago)
- Ignoring the numerous forms of undefined behavior that casting away `const` might invoke, the blunt but simple and standard solution is just to cast to `(void*)`.
- ```c
char* foo(const struct t *r)- {
return (void*)r->s;- }
- ```
- This is far more portable than gcc extensions like `typeof`.
- (C23 might introduce various type-related features similar to `_Generic` so there might be more elegant ways coming soon.)
- The only application for these kind of dirty casts is pretty much when dealing with broken API functions that take const-correct parameters but return a non-const pointer, like for example:
- char *strstr (const char *s1, const char *s2);
- This function is broken by design - always was. Correct design would be to return an index instead of a pointer. But if you are stuck with a broken API such as this one and have to implement it, you have to take shortcuts like casting away const.
- Ignoring the numerous forms of undefined behavior that casting away `const` might invoke, the blunt but simple and standard solution is just to cast to `(void*)`.
- ```c
- char* foo (const char* str)
- {
- return (void*)str;
- }
- ```
- This is far more portable than gcc extensions like `typeof`.
- (C23 might introduce various type-related features similar to `_Generic` so there might be more elegant ways coming soon.)
- The only application for these kind of dirty casts is pretty much when dealing with broken API functions that take const-correct parameters but return a non-const pointer, like for example:
- char *strstr (const char *s1, const char *s2);
- This function is broken by design - always was. Correct design would be to return an index instead of a pointer. But if you are stuck with a broken API such as this one and have to implement it, you have to take shortcuts like casting away const.
#1: Initial revision
by
Lundin
·
2022-06-15T19:53:47Z (over 2 years ago)
Ignoring the numerous forms of undefined behavior that casting away `const` might invoke, the blunt but simple and standard solution is just to cast to `(void*)`.
```c
char* foo(const struct t *r)
{
return (void*)r->s;
}
```
This is far more portable than gcc extensions like `typeof`.
(C23 might introduce various type-related features similar to `_Generic` so there might be more elegant ways coming soon.)
The only application for these kind of dirty casts is pretty much when dealing with broken API functions that take const-correct parameters but return a non-const pointer, like for example:
char *strstr (const char *s1, const char *s2);
This function is broken by design - always was. Correct design would be to return an index instead of a pointer. But if you are stuck with a broken API such as this one and have to implement it, you have to take shortcuts like casting away const.